There's certainly enough blame to go around.
Chancellor Katehi shouldn't have called in the campus police to dismantle the students' tents in the first place. As the Chancellor of a center for higher education, she should have encouraged the students to particpate in peaceful protest and the expression of their concerns. If she were truly concerned with the students' safety, which she claims was her reason for removing the tents from the quad, she should have sent the campus police to PROTECT the students during the execution of their freedom of speech.
The campus police should not have been confrontational. These were unarmed students who, by most accounts, were peaceful until the police showed up in full riot gear to tear down their tents. There was no immediate or imminent threat posed by the tents, so there was no need to rush in like an assault force to raze the camp. They could have taken the time to reason and negotiate with the students to remove the tents on their own. Had the police use their negotiation skills to diffuse the situation, there would probably have been no need to use force.
The students are not blameless, either. They should have shown some common sense and restraint. I fully support the students' right to protest and to use Civil Disobedience against what they (and I) felt was an unlawful order to cease the lawful execution of their right to free speech. However, they should not have moved to surround the police. Nor should they have chanted "If you let them go, we will let you leave."
Whether they were in any position to detain the heavily armed police force or not, and whether the police truly felt threatened by the unarmed students, is irrelevant. By chanting that implied but obviously empty threat, they weakened their moral superiority, tarnished their image as peaceful protestors, and gave the police an excuse to use force.
However, whether you feel the police were justified in using non-lethal force in that situation, the police are still guilty of using excessive force
because they used the pepper spray in violation of the manufacturer's guidelines. First, the campus police used a 1.3 percent solution, which, according to the manufacturer, is meant to stop a bear. The authorized dose for tactical deployment is 0.2 percent. Second, the campus police sprayed it directly into the students' faces and mouths at a point blank range while the manufacturer guidelines say 6 feet is the minimum distance for use. To quote Karam Logham, the man who helped develop pepper spray into a weapons-grade material in the 1980s: “I have never seen such an inappropriate and improper use of chemical agents.”